The trombone is a
brass instrument that was devised in the 15th century some time probably by the
Italians. The first reliable depiction of the trombone is in a
painting that is dated at 1490. Trombone is a derevitive of the Italian word tromba (trumpet) meaning big trumpet.
Throughout time there have been a number of types of trombones. Nowdays, however, we only have four main types: The alto, tenor, bass, soprano and valve. I have seen a valve, but I don't really know how it works
They are rather similar, but instead of a slide you have buttons that you press that make the pipe longer. My music teacher had another type of trombone that he called a 'bass trombone', but after researching it, 'bass trombone' is not the proper name for it. But I can't find the real name for it either =( It's essentially a normal trombone that has a lever. When you pull this lever the air is passed through more pipe thus making the notes lower.
So how does a trombone work? Well, a trombone, unlike any other instruments, has a slide that can move about to make the trombone longer or shorter. By doing this you are making the pipe that the air has to go through longer. A longer pipe means a lower note.
The trombone has seven positions each a semi-tone apart. For example, my tenor trombone can play an 'F' in the first position and if I move it out to the second it'll play an 'E' and if I move it out again it'll play an 'E flat'. Of course the trombone isn't only limited to seven notes in the chromatic scale, it can get different harmonics (See harmonic series too). For example, in my first position I can get a 'B flat', another 'B flat','F','B flat','D','F','A','B flat','C' and then it starts getting really hard. To understand how I can get so many notes in just one position, lets look at how you play the trombone.
If you put your lips together and 'buzz' them into a trombone you will get a sound. This sound travels through the mouthpiece, down the slide, up the 'U bend' and then out of the bell. As that buzzing sound goes through the instrument it sets up a standing wave system that makes a note. You can't get notes who's wavelength can't fit into the tube hence the intervals between each of the notes in first position. You see, if I try to play, say, a 'G' in first position I would only hit an 'F'. It's not possible to play a 'G' in first, you'd have to go out to forth. To get a higher harmonic I just tighten my lips and make a higher pitched buzzing sound.
The trombone is mainly used as a bass instrument. It reads most of it's music in bass cleff. I have been told that the trombone really brings out the life of a piece in our band. I tend to agree. The trombone has a very strong sound if played correctly. However, to master a trombone you really have to practise!